This invention relates generally to filter devices and, more particularly, to water system filters for small particulate contaminants.
It is well-known that the mechanical cleaning of a filter surface can be accomplished by having a brush or scraper drag along the filter surface where deposits have accumulated. In certain configurations, the brush or scraper is mounted at one end between two walls but with a significant portion of the brush or scraper projecting beyond the walls. Such configurations are shown in U.S. Pat. Nos. 148,557 (Gillespie et al.); 556,725 (Farwell); 740,574 (Kohlmeyer) and 793,720 (Godbe). In conventional filter systems, the particulate contaminants are driven off the filter surface and are deposited in a hopper or tank along with the fluid being filtered, thus discarding large amounts of the fluid being filtered.
The use of a brush, or high speed cleaning spray, disposed between a pair of walls for cleaning a cylindrical filter is known in the art, as is disclosed in U.S. Pat. Nos. 5,423,977 (Aoki et al.) and 5,595,655 (Steiner et al.) and Swiss Patent No. 22,863 (Zingg). Another variation employs a backwash that drives the particulate contaminants off of the cylindrical filter, as is disclosed in U.S. Pat. No. 3,338,416 (Barry).
An exemplary use of such filters is in a water desalination system that is available on ships. Shipboard water/salt water straining is a specialized straining process. In particular, the water/salt water flow is initially pre-strained for gross particulate contaminants, such that any particulate contaminants remaining in the water/saltwater flow are extremely small (e.g., <100 microns, with a large percentage being less than 25 microns). As a result, where these small particulate contaminants are captured by a downstream strainer (e.g., a wedge wire screen strainer), both on and within the strainer surface, and then later dislodged during the strainer cleaning process, these extremely small particulate contaminants do not fall by gravity toward a drain but remain suspended in the water/salt water and will re-attach to the strainer surface. Therefore, there remains a need for a cleaning device that can dislodge such extremely small particulate contaminants off of the downstream strainer surface, as well as from within the strainer surface, and then ensure that these particulate contaminants flow out through the drain rather than re-attaching to the strainer surface.
Thus, there is a need for an improved system for removing undesired particulate contaminants from a water/salt water flow and without interrupting that water/salt water flow to the engines, while minimizing the amount of fluid removed therewith. It is to just such a system that the present invention is directed.